1. Field of the Invention
The present invention relates to a magnetic head suspension for supporting a magnetic head slider that reads and/or writes data from and to a recording medium such as a hard disk drive.
2. Related Art
A magnetic head suspension that supports a magnetic head slider is required to rapidly and accurately have the magnetic head slider positioned at a center of a target track.
More specifically, the magnetic head suspension is directly or indirectly connected at a proximal side to an actuator such as a voice coil motor and swung around a swing center by the actuator so as to move the magnetic head slider, which is supported at a distal side of the suspension, to the center of the target track along a seek direction parallel to a disk surface.
In order to rapidly have the magnetic head slider positioned at the target track, it is needed to raise frequency of a driving signal for the actuator.
Accordingly, in order to allow the magnetic head slider to be moved to the target track in a rapid and accurate manner, it is desirable to prevent occurrence of resonant vibration of the magnetic head suspension as much as possible at the time when having the magnetic head suspension swung around the swing center.
Each of Japanese Unexamined Patent Publication Nos. 2005-032393 and 2008-021374 discloses a magnetic head suspension with a load beam part that is provided with paired flange portions over substantially entire region with respect to a suspension longitudinal direction.
The paired flange portions are useful in enhancing rigidity while preventing mass from increasing, thereby effectively increasing a resonant frequency.
Japanese Unexamined Patent Publication No. 2009-295261 (hereinafter referred to as JP'261) discloses a magnetic head suspension having a following configuration with the aim of minimizing displacement amount (gain) of the magnetic head slider in the seek direction at the time when the magnetic head suspension is vibrated while realizing an effect of increasing the resonant frequency thanks to the paired flange portions provided at the load beam part. That is, the load beam part with the paired flange portions is bent around two bending lines including a distal-side bending line that is positioned at substantially center in the suspension longitudinal direction and extends along a suspension width direction, and a proximal-side bending line that is positioned closer to a proximal side in the suspension longitudinal direction than the distal-side bending line and extends along the suspension width direction.
More specifically, vibration modes that occur in the magnetic head suspension include a main resonance mode that vibrates in the seek direction, a bending mode that vibrates in z direction perpendicular to the disk surface, and a torsion mode that vibrates in a twisting manner around a suspension longitudinal center line.
When a vibration occurs in the magnetic head suspension, the magnetic head slider is displaced from the target track in accordance with a level of the vibration. A displacement amount (gain) of the magnetic head slider at the time when the suspension vibrates in the torsion mode can be minimized by bending the load beam part around a bending line along the suspension width direction and adjusting the bending angle at the bending line to an optimum value.
That is, bending of the load beam part with an optimum bending angle makes it possible to effectively prevent the magnetic head slider from being displaced from the target track even if the vibration of the torsion mode occurs in the magnetic head suspension.
The magnetic head suspension disclosed by JP'261 has been made in view of this point, and can minimize the gain of the magnetic head slider by setting the bending angles at the distal-side bending line and the proximal-side bending line to the respective optimum values while realizing the effect of increasing the resonant frequency thanks to the paired flange portions.
Although the magnetic head suspension disclosed by JP'261 can minimize the gains of the magnetic head slider with respect to the first and second torsion modes, the gain in the third torsion mode has not been taken into consideration.
More specifically, when the frequency of the driving signal for the actuator reaches a certain frequency (a first resonant frequency), a resonant vibration in the first torsion mode occurs in the magnetic head suspension.
In a case where the frequency of the driving signal is further raised beyond the first resonant frequency, upon reaching another certain frequency (a second resonant frequency), a resonant vibration in the second torsion mode occurs in the magnetic head suspension. In a case where the frequency of the driving signal is still further raised beyond the second resonant frequency, upon reaching still another certain frequency (a third resonant frequency), a resonant vibration in the third torsion mode occurs in the magnetic head suspension.
In particular, it is needed to raise the frequency of the driving signal for the actuator that drives the magnetic head slider in order to speed up the reading/writing action by the magnetic head slider, as explained earlier. Therefore, it is needed to take measures the vibration of the third torsion mode as well as the vibrations of the first and second torsion modes with respect to the displacement of the magnetic head slider due to the vibration of the torsion mode.
In view of this point, the magnetic head suspension disclosed by JP'261 leaves room for improvement.
JP'261 also discloses a magnetic head suspension according to a modified embodiment in which the paired flange portions are provided with cutouts or through holes at positions where the distal-side bending line and the proximal-side bending line are arranged.
The modified embodiment can facilitate the bending processes around the distal-side bending line and the proximal-side bending line in comparison with a configuration without the cutout or the through hole.
However, the modified embodiment remains a problem that the paired flange portions have to be deformed upon the bending processes around the distal-side bending line and the proximal-side bending line.
In particular, in order to make an amount in which the gain can be adjusted by means of the bending process around the proximal-side bending line same as an amount in which the gain can be adjusted by means of the bending process around the distal-side bending line, it is needed to make the bending angle at the proximal-side bending line, which is positioned closer to a proximal side in the suspension longitudinal direction than the distal-side bending line, larger than that at the distal-side bending line. As a result, there is a problem that the accurate bend process around the proximal-side bending line is made difficult.
More specifically, ranges in which the gain of the magnetic head slider can be adjusted by means of the bending processes around the distal-side bending line and the proximal-side bending line depend on displacement amounts resulted from the bending processes around the respective bending lines. The displacement amount means a displacement height which is a difference between height positions at which the magnetic head slider is positioned before and after the bending process is made, respectively.
Assuming that a displacement height “H” is achieved by bending the load beam part around the distal-side bending line, which is positioned at a substantially center in the suspension longitudinal direction, with a bending angle “A”, it is needed to bend the load beam part, which is positioned closer to a proximal side in the suspension longitudinal direction than the distal-side bending line, with a bending angle larger than the bending angle “A” in order to achieve the same displacement height “H” by means of the bending process around the proximal side bending line. Bending the load beam part with the larger angle causes the paired flange portions to be largely deformed.